PN 537465 Fwd Engine Mount Thru bolt stripped (split topic).

How to keep the Cessna 170 flying and airworthy.

Moderators: GAHorn, Karl Towle, Bruce Fenstermacher

Post Reply
User avatar
skifast13
Posts: 14
Joined: Tue Mar 02, 2021 10:57 pm

PN 537465 Fwd Engine Mount Thru bolt stripped (split topic).

Post by skifast13 »

Question regarding thru bolt 537465 (corrected). Attached is a pic of my right front engine mount. While conducting oil leak mitigation my thru bolt snapped under far less than 400 inch pounds of torque. Bolt that snapped is circled. The bolt that was installed on my block does not appear to be the item depicted as compared to the X30014 Illustrated Parts Manual Figure 2 Item 12. Mine was a long bolt, it was not threaded on both sides. Are your front mounts set up similarly or do (did) I have the completely wrong thru bolt in my block?

Thanks folks! Hope to meet some of you at EAA 2022 - Wisconsin is my home state.
IMG_1124.jpg
Miles
Last edited by skifast13 on Thu Dec 30, 2021 1:43 pm, edited 1 time in total.
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

Re: Looking for reasonably priced 531211 & 537466 through bo

Post by Bruce Fenstermacher »

Miles, I've rebuilt 2, 0-300s and a C-85. I work on larger TCM and Lycoming engines daily. No, I haven't seen every type of thru (or through) bolt, and I've slept a night or two since viewing a 0-300. The circled bolt does not look like any thru bolt I've ever installed or retorqued. I'd lean very heavily in the direction that is definitely not a thru bolt.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
User avatar
GAHorn
Posts: 20967
Joined: Fri Apr 12, 2002 8:45 pm

Re: Looking for reasonably priced 531211 & 537466 through bo

Post by GAHorn »

skifast13 wrote:Question regarding thru bolt 537466. Attached is a pic of my right front engine mount. While conducting oil leak mitigation my thru bolt snapped under far less than 400 inch pounds of torque. Bolt that snapped is circled. The bolt that was installed on my block does not appear to be the item depicted as compared to the X30014 Illustrated Parts Manual Figure 2 Item 12. Mine was a long bolt, it was not threaded on both sides. Are your front mounts set up similarly or do (did) I have the completely wrong thru bolt in my block?

Thanks folks! Hope to meet some of you at EAA 2022 - Wisconsin is my home state.
IMG_1124.jpg
Miles
(I believe you’ve inadvertently made a “typo”…. I believe you meant PN 537465…..which is item 12, Fig 2. And, No…that doesn’t look right at all.
I sent you a PM earlier about a picture before I saw this post. I’d like to see the rest of that incorrect bolt, and expecially a close-up of where it snapped.
(and per the PM, the addt’l info also, pls.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
skifast13
Posts: 14
Joined: Tue Mar 02, 2021 10:57 pm

Re: Looking for reasonably priced 531211 & 537466 through bo

Post by skifast13 »

You’re absolutely correct, George, I meant to type 537465. I’ll provide the requested info after this wknd. We’re hosting NYE so won’t be able to get to hangar until next week.
User avatar
cessna170bdriver
Posts: 4059
Joined: Mon Apr 22, 2002 5:13 pm

Re: Looking for reasonably priced 531211 & 537466 through bo

Post by cessna170bdriver »

IIRC, at least some if not all of the through bolts have provisions for o-rings near the case split, which if true, the case needs to be apart for proper installation of the o-rings. I have heard of some success with putting o-rings under the nuts at the outboard ends of the bolts to correct oil leaks.

Excuse me if you already know this, but be sure to torque BOTH ends of all through bolts when installing them.
Miles

“I envy no man that knows more than myself, but pity them that know less.”
— Thomas Browne
User avatar
GAHorn
Posts: 20967
Joined: Fri Apr 12, 2002 8:45 pm

Re: Looking for reasonably priced 531211 & 537466 through bo

Post by GAHorn »

cessna170bdriver wrote:

Excuse me if you already know this, but be sure to torque BOTH ends of all through bolts when installing them.
Miles Bowen makes an excellent point…and I’ll add that twisting/torque-ing one side at a time has its’ hazards…. It can pull the bolt off-center and dislodge that O-ring (on Through-bolts which have O-rings, of course)…. and it’s a good technique to keep a wrench on the opposite end of the thru-bolt to prevent that shift while torque-ing.
<edited>

Aaannnddd…. before we get to jumping too far to conclusions…. there may be a superceded part involved here… I’m researching it now…but so-far it may be that the lower/forward fastener actually is a bolt with a head on one end…and drilled for a cross-pin on the other end. I’ve got a call into one of our Members who has recently been into this to see what we can discover.
3EEB561C-914A-47A3-AC58-135F23374F10.png
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
GAHorn
Posts: 20967
Joined: Fri Apr 12, 2002 8:45 pm

Re: Looking for reasonably priced 531211 & 537466 through bo

Post by GAHorn »

Ok, after doing some research it appears the Illustrated Parts Catalog “depictions” of certain parts is INcorrect.

It seems the thru-bolt being discussed, which inserts thru the lower/front of the engine mount bracket is actually a “headed” bolt…with a threaded-end for a nut being cross-drilled for a pin (split pit/cotter). There is an O-ring at EACH end beneath the head and nut to restrict oil seepage.

The PN is 537465.

Miles, it also appears you do not have to split your engine to make this repair. You should be able to drive out any remaining parts of the thru-bolt…and replace it with another.

And HERE is your Christmas Gift!!!! I have a source for one at a price which will make you a VERY HAPPY GUY! (Contact me)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
Post Reply